In rolling bearing technology it is commonly known that deep-groove ball bearings are rigid, permanently assembled radial rolling bearings, which are distinguished by an equally high radial and axial load bearing capacity, and which by virtue of their low friction have the highest speed limits of all types of bearings. These deep-groove ball bearings substantially comprise an outer bearing ring and an inner bearing ring and a number of balls, which as rolling elements are arranged between the bearing rings and which roll on groove-shaped ball raceways recessed into the inside of the outer bearing ring and into the outside of the inner bearing ring, and are guided at uniform distances from one another by a bearing cage. Filling radial ball bearings with the balls is in this case performed by the eccentric assembly method disclosed by DE 168 499, in which the two bearing rings are arranged eccentrically in relation to one another and the resulting crescent-shaped free space between the bearing rings is filled with the balls. The size and number of the balls are in each case designed according to the size of the bearing, so that the inner bearing ring between the first and last ball can be brought into the position concentric to the outer bearing ring using the elasticity of the two bearing rings, so that the balls can finally be distributed at a uniform distance from one another on the pitch circle of the two ball raceways and the bearing cage can be inserted.
In practice it has proved, however, that limits are nevertheless placed on the load-bearing capacity of such deep-groove ball bearings, owing to the low maximum number of balls that can be fitted or the low maximum filling density of approximately 60%. In the past a plurality of solutions have therefore been proposed, such as an unclosed insertion aperture arranged in the opposing flanges of the outer and inner bearing ring according to DE 151 483, for example or a closable insertion aperture of similar design according to DE 24 07 477 A1, which by increasing the number of balls are intended to increase the filling density and hence the load-bearing capacity of deep-groove ball bearings. Both in the unclosed and in the closed embodiment, however, such insertion apertures have the disadvantage that due to their wedge-shaped opening into the raceways of the balls or due to burrs a “sticking” or jamming of the rolling elements can occur at this insertion aperture, so that in practice such solutions have failed to gain acceptance.
Another possible way of increasing the number of rolling elements on a radial rolling bearing has also been disclosed by DE 43 34 195 A1. In this radial rolling bearing, intrinsically embodied as a single-row, deep-groove ball bearing, however, the rolling elements are not formed by balls but by so-called ball rollers, which are designed with two lateral faces symmetrically flattened from a basic spherical shape and arranged parallel to one another. The width of these ball rollers between their lateral faces is here less than the distance between the inside of the outer bearing ring and the outside of the inner bearing ring, so that the bearing can be filled with the ball rollers by the so-called axial assembly method, in which the ball rollers can be introduced into the bearing horizontally, as it were, axially through the distance between the inner and the outer bearing ring. When the centre of the ball rollers is then situated on a level with the axis of the rolling element raceway, the ball disks are turned by 90°, so that they are able to roll in the rolling element raceways with their ball bearing surfaces.
Despite the possibility for inserting these specially designed ball rollers axially into the bearing, thereby allowing the radial rolling bearing to be filled with a large number of rolling elements, however, such a radial rolling bearing at most only represents a compromise in terms of the desired increase in the load-bearing capacity of the bearing. This is due to the fact that the ball rollers, owing to their capability for axial introduction into the bearing, can only be formed with a correspondingly small width between their lateral faces, in order that they may be readily introduced into the bearing through the distance between the inner and the outer bearing ring. The rolling element raceways in the bearing rings can likewise be only of relatively shallow and narrow design, so as to be able to turn the rolling elements into their operating position without producing excessive radial play throughout the bearing in this operating position. However, the relatively narrow ball rollers and the shallow rolling element raceways give rise to a relatively small contact area of the ball rollers with their rolling element raceways, so that both the axial and the radial load-bearing capacity of such a radial bearing is again reduced and the original advantage of the increased number of rolling elements is almost entirely offset.
In order to avoid these disadvantages it has therefore been proposed by DE 10 2005 014 556 A1 to increase the width of the ball rollers between their lateral faces to at least 70% of the diameter of their basic spherical shape and to form the grooved raceways in the bearing rings with a depth of approximately 19% and a width of approximately 75% of the diameter of the basic spherical shape of the ball rollers, since this gives rise to an overall contact area of the ball rollers with their raceways amounting to approximately 45% of the circumference of the basic spherical shape of the ball rollers, as the balls of conventional deep-groove ball bearings with regard to their raceways in the bearing rings also exhibit. Since the distance between the outside of the inner bearing ring and the inside of the outer bearing ring is thereby reduced to approximately 60% of the diameter of the basic spherical shape of the ball rollers, however, and is therefore less than the width of the ball rollers, their insertion into the radial rolling bearing has again been accomplished by the eccentric assembly method, in which the ball rollers, with their lateral faces adjacent to one another are inserted obliquely into the raceways, into the free space between the two bearing rings, arranged eccentrically in relation to one another, before bringing the inner bearing ring into the position concentric with the outer bearing ring and finally distributing the ball rollers with a uniform distance between them on the pitch circle of their raceways and swivelling them by 90°. The flattened lateral faces of the ball rollers here mean that even with the eccentric assembly method it is possible to insert a greater number of rolling elements into the ball roller bearing compared to single-row, deep-groove ball bearings, giving a filling density of 73%.
Although a ball roller bearing of such a design has proved successful in giving the ball rollers large contact areas with their raceways in the bearing rings, in a manner similar to the balls of a deep-groove ball bearing, and allowing the ball roller bearing to be fitted with greater number of rolling elements or a higher filling density than conventional single-row, deep-groove ball bearings, the eccentric assembly method nevertheless means that some reductions in the number of rolling elements nevertheless have to be made compared to the greater number of rolling elements feasible in the axial assembly method. Although it has therefore been possible to reduce the overall axial installation space and the weight of the ball roller bearing compared to conventional deep-groove ball bearings and to increase its axial load-bearing capacity, the increase in the radial load-bearing capacity of the ball roller bearing nevertheless proved to be comparatively slight.